Evaluation of guaiacyl lignin aromatic structures using 13CO2 administered Ginkgo biloba L. xylem by quantitative solid- and liquid-state 13C NMR

Ginkgo biloba L. saplings were cultivated in an airtight growth chamber with (CO2)-C-13 for two months. The C-13 ratio of the newly developed xylem region was ca. 85%, evaluated by high lateral resolution secondary ion mass spectrometry and thioacidolysis/GC-MS. Quantitative solid-state C-13 direct polarisation/magic angle spinning (DP/MAS) NMR measurements with high-speed MAS of 70.0 kHz were conducted for cutting-milled wood (CMW), ball-milled wood (BMW), and enzymatically saccharified lignin (EL) samples. In addition, quantitative liquid-state C-13 NMR measurements were carried out for EL in DMSO-d(6). Major lignin aromatic signals were classified into three groups of aromatic carbons of C-H, C-C, and C-O, and their area ratio was compared within these measurements. EL samples in solid- and liquid-state showed nearly the same results. However, the results for CMW and BMW in solid-state NMR suggest the structural alteration of lignin within the sample preparation procedure, including ball milling.